We describe the design of tangible interfaces to the KidPad collaborative drawing tool. Our aims are to support the re-enactment of stories to audiences, and integration within real classroom environments. A six-month iterative design process, working with children and teachers in school, has produced the "magic carpet", an interface that uses pressure mats and video-tracked and barcoded physical props to navigate a story in KidPad. Reflecting on this process, we propose four guidelines for the design of tangible interfaces for the classroom. (1) Use physical size and physical props to encourage collaboration. (2) Be aware of how different interfaces emphasize different actions. (3) Be aware that superficial changes to the design can produce very different physical interactions. (4) Focus on open low-tech technologies rather than (over) polished products.

We describe the iterative design of two collaborative storytelling technologies for young children, KidPad and the Klump. We focus on the idea of designing interfaces to subtly encourage collaboration so that children are invited to discover the added benefits of working together. This idea has been motivated by our experiences of using early versions of our technologies in schools in Sweden and the UK. We compare the approach of encouraging collaboration with other approaches to synchronizing shared interfaces. We describe how we have revised the technologies to encourage collaboration and to reflect design suggestions made by the children themselves.

Techniques for improving the imageability of an existing data visualisation are described. The aim is to make the visualisation more easily explored, navigated and remembered. Starting from a rclatively sparse landscape-like representation of a set of objects, we selectively add to the visualisation static features such as clusters, and dynamic features such as view-specific sampling of object detail. Information on past usage is used in this process, making manifest an aspect of interaction which is often neglected. Issues arising from the use of such features in a shared virtual environment are discussed.

Room metaphors have become increasingly popular as a basis for CSCW systems. The paper describes how such metaphors might be extended to support large scale communication through the introduction of a spatial model for mediating conversations in virtual computer spaces. The model is described in terms of an abstract mathematical framework and the paper then outlines how this might be applied to various kinds of CSCW system. As a next step, the combination of rooms into larger virtual structures is considered and this results in proposals for structuring, navigating and mapping a large virtual cyberspace for cooperation. Finally, the paper describes a current prototype application and reflects on some of the architectural issues involved in its realisation as a distributed system.